The invention relates to a process, and to a device for performing the process, for casing a book block or paper-cover block into a cover during the manufacture of adhesively bound books, paper covers and magazines in an adhesive binding machine.
In an adhesive binding machine for manufacturing books, paper covers or magazines, leaves or folded sheets which have been gathered together are transported, with a defined hanging-out portion, in block clamps belonging to a transport system, and are connected to form a book block or paper-cover block by the application of an adhesive to the machined back of the block. The connection of a scored cover to the book block or paper-cover block which has previously been provided with a lateral coating of glue, the so-called xe2x80x9ccasing-inxe2x80x9d operation, takes place in a cover laying-on and pressing-on arrangement, the said cover being pressed against the back of the block and adjoining side regions during the continuous movement of the book block or paper-cover block.
Instead of the normal procedure of coating the spine of the block which are used herein refers to the back of the block and/or its adjoining side regions with glue by means of rollers and discs, the adhesive can also be applied to the cover using nozzles, in a manner corresponding to the breadth of the back of the block and of the side regions to be coated with glue.
As a result of various correlations and influences in the pre-production process, a more or less pronounced expansion occurs in the back of the block, the so-called xe2x80x9cmushroom formationxe2x80x9d, which may also have an asymmetrical shape. As experience shows, this not infrequently leads, when the cover and block are joined, to inaccurate centring of the back of the block in relation to the scoring on the cover or in relation to the bent edges. The consequence of this is an inferior quality of the product, such as an unsightly shape for the back, a title impression which extends at an angle in relation to the edge of the back, and also the formation of folds on the first and last pages of the block when the cover is pressed on laterally. The said formation of folds can also occur in so far as the pressed-on sides of the cover, after being released by the pressing-on station, detach themselves from the adhesive bond, together with the first and last pages, as a result of the recovery forces of the cover. Because of the sticking power of the adhesive between the applying discs of the adhesive-applying device and the sides of the block, there is also the risk, particularly in the case of thin papers, of the outer leaves or layers coming off the block, something which can likewise entail the formation of folds during the pressing-on operation. All this not only affects the quality of the books, paper covers or magazines, but also has an adverse effect on the adhesion.
The object of the invention consists in proposing, while avoiding the disadvantages of the prior art, a process for casing a book block or paper-cover block into a cover during the manufacture of adhesively bound books, paper covers or magazines in an adhesive binding machine, and a device for performing the said process, with the aid of which process and device a substantial increase in the quality of the products can be made possible.
This is achieved by means of the invention in a surprisingly simple manner through the fact that, according to a first idea of the invention, the hanging-out portion of the block is aligned with the back region, which is preferably predetermined by scoring, of a cover which is fed in, and the said cover is pressed against the spine of the block which includes the back and/or the side regions of the block.
According to a second idea of the invention, the block is coated with glue on the back, the hanging-out portion is optionally aligned with the back region of the cover which is fed in, the said cover is pressed against the back, and the side regions of the block or of the cover are thereupon coated with glue and the cover is pressed on laterally.
In order to perform the process, a centring arrangement is provided which acts, from opposite sides, on the hanging-out portion of a block transported in a block clamp belonging to an adhesive binding machine, and aligns the said block with the centre of the block clamp. Further features of the process and device emerge from the dependent claims.
With the aid of the process and of the device for performing the process, it is possible to manufacture adhesively bound books, paper covers or magazines, which are of high quality in respect of both aesthetics and also physical properties. It is particularly advantageous if, before the cover is pressed on, the hanging-out portion of the book block or paper-cover block is aligned, in a positionally precise manner, with the back region of the cover, which back region is preferably predetermined by scoring. As a result of this, the first and last pages of the book block or paper-cover block are always located exactly between the scoring on the back.